Field of the Invention
The present invention relates to compounds useful in a variety of applications, including materials of various types of optical members such as optically anisotropic films and heat shield films, and to liquid crystal compositions and polymer materials containing such compounds. The invention also relates to films that use such materials.
Background Art
Liquid crystals orderly align themselves upon being applied onto a film subjected to an alignment process (alignment film). The alignment state of liquid crystal can be controlled with the use of two alignment films disposed on the both sides of the liquid crystal. An example of such a structure is a liquid crystal display device that includes a liquid crystal cell constructed from rod-like liquid crystal molecules and a pair of substrates sealing the liquid crystal molecules, and an electrode layer provided to apply voltage to the rod-like liquid crystal molecules. In such a liquid crystal display device, the rod-like liquid crystal molecules are injected into the gap between the alignment films formed on the two substrates, and the alignment state of the rod-like liquid crystal molecules can be controlled relatively easily.
On the other hand, it has been proposed to dispose an optical compensation sheet (retardation plate) between a liquid crystal cell and a polarizing plate for the purpose of increasing the viewing angle or preventing coloring of a liquid crystal display device. In this case, an optically anisotropic element having an optically anisotropic layer formed from liquid crystal molecules is used as an optical compensation sheet on a transparent support. The optically anisotropic layer is formed by aligning liquid crystal molecules, and fixing the alignment state. Here, the liquid crystal molecules are aligned with a single alignment film provided between the transparent support and the optically anisotropic layer. However, it is difficult with a single alignment film to uniformly align (monodomain alignment) the liquid crystal molecules from the alignment film interface to the air interface. This is because of the disturbed liquid crystal alignment due to the lack of alignment regulation on the side of the interface (air interface) not subjected to an alignment process. Non-uniform alignment of liquid crystal molecules causes scattering of light due to disclination, and a nontransparent film is formed. Such a film is not desirable from the standpoint of improving the viewability of the liquid crystal display device.
Out of these needs, a technique is developed that regulates alignment of a liquid crystal and uniformly aligns the liquid crystal also on the side of the interface (air interface) not subjected to an alignment process, without using an alignment film (Patent Reference 1). In this technique, alignment of the liquid crystal molecules is controlled by adding a liquid crystal alignment promoting agent that has a discotic core and terminal long-chain fluorinated alkyl. By using the liquid crystal alignment promoting agent, a liquid crystal composition is provided that allows liquid crystal molecules to uniformly align themselves with ease.